Method of processing substrate

ABSTRACT

A method of processing a substrate to enable selective doping without a photolithography process is provided. The method includes forming a diffusion barrier on the substrate having a patterned structure using plasma deposition method, removing the diffusion barrier except for part of the diffusion barrier using wet etching, forming a diffusion source layer on the patterned structure and the part of the diffusion barrier, and applying energy to the diffusion source layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/367,569, filed on Jul. 27, 2016 and U.S. Provisional Application No. 62/371,577, filed on Aug. 5, 2016, in the United States Patent and Trademark Office, the disclosures of which are incorporated herein in their entirety by reference.

BACKGROUND

1. Field

One or more embodiments relate to a method of processing a substrate, and more particularly, to a method of depositing a thin film on a silicon substrate having a step structure.

2. Description of the Related Art

Conventional thin film deposition techniques are about uniformly depositing a thin film on a silicon substrate having a step structure. In detail, various processing techniques have been developed with the goal of realizing a step coverage of nearly 100% by depositing a thin film on the top, side, and bottom of the step structure to have a uniform thickness. However, the conventional deposition techniques have difficulties in realizing selective etching or selective doping on the top, side or bottom of the step structure. Therefore, a new deposition technique is desired to allow the selective etching or doping.

SUMMARY

One or more embodiments include a method of realizing selective etching and/or selective doping on a film deposited on a step structure of a silicon substrate.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.

According to one or more embodiments, a method of processing a substrate includes preparing a structure comprising a first surface and a second surface having a slope with respect to the first surface, forming a first layer on the structure by applying plasma to densify or embrittle at least part of the first layer, isotropically etching the first layer so that at least a part of the first layer remains as a remnant, forming a second layer containing a dopant on the structure and the remnant of the first layer, and diffusing the dopant into the structure.

The dopant may not be diffused into a portion corresponding to the remnant of the first layer in the structure.

The first layer may be patterned by the forming of the first layer and the isotropic etching of the first layer without a separate photolithography process.

A location of the remnant of the first layer may be controlled by at least one plasma process parameter used during the forming of the first layer.

The first layer on the first surface may be maintained and the first layer on the second surface may be removed by the isotropic etching.

The first layer on the first surface may be maintained due to an ion bombardment effect.

Alternatively, first layer on the first surface may be removed and the first layer on the second surface may be maintained by the isotropic etching.

The first layer on the first surface may be removed due to hydrogen active species injected during the applying of the plasma.

The method may further include forming a third layer on the second layer after the forming of the second layer and before the diffusion of the dopant.

The first layer may include a silicon nitride layer and the second layer may include a silicate glass layer.

The method may further include removing the remnant of the first layer and the second layer.

The first layer and the second layer may include different materials. The removing of the remnant of the first layer and the second layer may include removing the second layer to expose the structure and the remnant of the first layer on the structure, forming a fourth layer on an exposed surface of the structure and the remnant of the first layer, using the same material as the first layer, and removing the remnant of the first layer and the fourth layer.

Plasma may be applied during the forming of the fourth layer to densify or embrittle at least part of the fourth layer.

The forming of the second layer may include a first cycle and a second cycle. The first cycle may include supplying a first source and purging the first source. The second cycle may include supplying a second source, purging the second source, and applying plasma in a state where a reactant has been provided.

According to one or more embodiments, a method of processing a substrate includes forming a diffusion barrier, comprising a first portion and a second portion having a slope with respect to the first portion, on a structure; applying plasma to densify or embrittle the first portion of the diffusion barrier; isotropically etching the diffusion barrier; forming a diffusion source layer on the structure and a remnant of the diffusion barrier; diffusing a dopant into the structure, and removing the diffusion source layer and the remnant of the diffusion barrier.

The first portion may be densified during the applying of the plasma. The first portion may remain and the second portion may be removed after the isotropic etching.

Alternatively, the first portion may be embrittled during the applying of the plasma. The first portion may be removed and the second portion may remain after the isotropic etching.

The applying of the plasma may be performed during the forming of the diffusion barrier.

The structure may include a first surface and a second surface. The diffusion barrier may directly contact one of the first and second surfaces and the diffusion source layer may directly contact the other of the first and second surfaces.

According to one or more embodiments, a method of processing a substrate includes forming a diffusion barrier on the substrate having a patterned structure using plasma deposition, removing the diffusion barrier except for part of the diffusion barrier using wet etching, forming a diffusion source layer on the patterned structure and the part of the diffusion barrier, and applying energy to the diffusion source layer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which:

FIGS. 1 through 3 are flowcharts of methods of processing a substrate, according to embodiments of the inventive concept;

FIG. 4 is a flowchart of a method of processing a substrate, according to one or more embodiments of the inventive concept;

FIG. 5 is a detailed diagram of a stage of depositing a silicon nitride layer in the method illustrated in FIG. 4;

FIG. 6 is a detailed diagram of a stage of depositing a phosphorous silicate glass (PSG) layer in a stage of depositing a boron silicate glass (BSG)/PSG layer in the method illustrated in FIG. 4;

FIG. 7 is a detailed diagram of a stage of depositing a capping oxide layer in the method illustrated in FIG. 4;

FIGS. 8A through 8H are schematic diagrams of a method of processing a substrate according to one or more embodiments of the inventive concept;

FIGS. 9A through 9H are schematic diagrams of a method of processing a substrate according to one or more embodiments of the inventive concept;

FIGS. 10 and 11 are transmission electron microscopy (TEM) photographs of the results of performing wet cleaning after depositing a silicon nitride layer under different conditions;

FIG. 12 is a diagram of a secondary ion mass spectroscopy (SIMS) result showing phosphorous (P) concentrations in a pattern before/after annealing according to existence or non-existence of a silicon nitride layer;

FIGS. 13 through 18 are schematic diagrams of a method of processing a substrate according to one or more embodiments of the inventive concept; and

FIGS. 19A through 20C are schematic diagrams of methods of processing a substrate according to one or more embodiments of the inventive concept.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description.

The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the inventive concept. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising” when used in this specification, specify the presence of stated features, numbers, steps, operations, elements, components, and/or groups thereof but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, regions, and/or parts, these elements, regions, and/or parts should not be limited by these terms. These terms are not used to define a particular order, hierarchy, or superiority but only used to distinguish one element, region, or part from another. Accordingly, a first element, region, or part could be termed a second element, region, or part without departing from the teachings of the disclosure.

Hereinafter, embodiments of the inventive concept will be described with reference to the accompanying drawings in which the embodiments are schematically shown. In the drawings, modifications of the shapes may be expected according to, for example, manufacturing techniques and/or tolerance. Accordingly, the embodiments should not be construed as being limited to the particular shapes illustrated herein and should be considered as comprising, for example, the changes in the shapes resulting from manufacturing processes.

A method of processing a substrate according to one or more embodiments will be described with reference to FIG. 1. FIG. 1 is a flowchart of a manufacturing method.

Referring to FIG. 1, a structure comprising a first surface and a second surface is prepared in operation S1 (see FIG. 8A). For example, a substrate having the structure may be loaded into a reactor of a deposition system. The second surface may have a slope with respect to the first surface. In detail, the second surface may be perpendicular to the first surface.

Thereafter, a first layer is formed on the structure in operation S2 (see FIG. 8B). The first layer may be a silicon oxide layer or a silicon nitride layer. In some embodiments, the first layer may function as a diffusion barrier which prevents impurities from entering the structure using energy application in following processes. For example, the first layer may include a metal layer or an insulating layer.

The first layer may be formed using a plasma atomic layer deposition process. In an embodiment, a cycle comprising a stage of providing a source and a stage of applying plasma in a state where a reactant has been provided may be performed at least once while the first layer is being formed. Purging may also be performed between the stage of providing a source and the stage of applying plasma and/or between cycles. The first layer may be formed using a different deposition process using plasma than the one described above.

Plasma applied during the formation of the first layer may have directivity. The first layer may be formed in a reaction space between a gas supply device, for example, a shower head, and a substrate supporting plate. During the application of plasma, the shower head may function as an upper electrode and the substrate supporting plate may function as a lower electrode. In this case, plasma may be generated due to a potential difference between the upper electrode and the lower electrode and the plasma may have directivity from the upper electrode to the lower electrode.

At least part of the first layer may be densified or embrittled during the formation of the first layer due to the directivity of the plasma moving from the shower head to the substrate supporting plate. For example, when the first layer has a top, a bottom, and a side connecting the top and the bottom, active species may collide mainly with the top and the bottom due to the directivity of the plasma. Accordingly, part of the first layer may be densified or embrittled according to a type of substance supplied during the application of plasma.

For example, when a material supplied during the application of plasma includes a large amount of a substance containing hydrogen (e.g., ammonia (NH₃)), a large amount of a hydrogen active species may be generated during the application of plasma. The hydrogen active species may move from the shower head to the substrate supporting plate and collide with the top and the bottom of the first layer, and therefore, the content of hydrogen in the first layer may be higher in the top and the bottom than in the side. This high hydrogen content may lead to embrittlement of a thin film.

On the contrary, when a material supplied during the application of plasma includes a small amount or none of a substance containing hydrogen (e.g., ammonia (NH₃)) or when a substance not containing hydrogen (e.g., nitrogen (N₂) or argon (Ar)) is supplied, the hydrogen content in the first layer may not change during the application of plasma and the first layer may be densified due to the collision of plasma active species. The densification of the first layer may result from an ion bombardment effect.

The first layer has different physical properties at different positions according to the formation (particularly, partial embrittlement and densification) thereof. Selective etching may be accomplished in a following isotropic etching process due to the different physical properties of the first layer at different positions.

Referring back to FIG. 1, after the first layer is formed on the structure, the first layer is isotropically etched in operation S3 (see FIG. 8C). The isotropic etching may be performed using a wet etching process and may be performed using phosphoric acid or hydrofluoric acid.

The isotropic etching may be performed so that at least part of the first layer remains. For example, an etch rate for a first part (e.g., the top and/or the bottom) of the first layer may be slower than an etch rate for a second part (e.g., the side) having a slope with respect to the first part of the first layer during the isotropic etching. Accordingly, the second part of the first layer may be removed, but the first part of the first layer may remain.

Since the first layer has different physical properties at different positions, the first part of the first layer has a different etch rate than the second part thereof. For example, a substance not containing hydrogen and/or a substance containing a component of a thin film (e.g., argon and/or nitrogen) may be supplied while plasma having directivity is being applied. In this case, the first layer (or the first part) on the first surface (e.g., the top surface or the bottom surface) of the structure perpendicular to the directivity is densified while the first layer (or the second part) on the second surface (e.g., the side surface) parallel to the directivity is not much affected, so that the second part may be selectively etched during a following isotropic etching process.

Consequently, the first layer on the first surface of the structure is maintained while the first layer on the second surface of the structure is removed by the isotropic etching. The first layer on the first surface may be maintained by an ion bombardment effect (i.e., the densification of the first layer on the first surface).

In another example, a substance containing hydrogen (e.g., ammonia) may be supplied while plasma having directivity is being applied. In this case, the first layer (or the first part) on the first surface (e.g., the top surface or the bottom surface) of the structure, which is perpendicular to the directivity, is embrittled while the first layer (or the second part) on the second surface (e.g., the side surface) parallel to the directivity is not much affected, so that the first part may be selectively etched during a following isotropic etching process.

Consequently, the first layer on the first surface of the structure is removed while the first layer on the second surface of the structure is maintained by the isotropic etching. The first layer on the first surface may be removed by the hydrogen active species injected during the application of plasma, as described above, (i.e., by the embrittlement of the first layer on the first surface).

As described above, when a method of processing a substrate, according to one or more embodiments of the inventive concept, is used, a first layer is patterned through a stage of forming the first layer and a stage of performing isotropic etching on the first layer without a separate photolithography process. In other words, the position of a remnant of the first layer on a structure may be controlled by at least one (e.g., a hydrogen content in a reactant) plasma process parameter used during the stage of forming the first layer, and therefore, a thin film may be selectively deposited on the structure having a step , using only plasma-involved deposition and isotropic etching (or wet etching) without a photolithography process.

After the first layer is isotropically etched, a second layer is formed on the structure and the remnant of the first layer in operation S4 (see FIG. 8D). The second layer may comprise a different substance than the first layer. For example, the second layer may comprise a dopant and may be a thin film used to form a doped region. The second layer may be a silicate glass layer comprising an impurity such as boron or phosphorus.

Alternatively, the second layer may not contain a dopant. In other words, the second layer may be an additional thin film formed on the structure and the first layer which has been formed on the structure at a selective position. The first layer may be a silicon nitride layer and the second layer may be a silicon oxide layer. Alternatively, the first layer may be a silicon oxide layer and the second layer may be a silicon nitride layer.

The second layer may be formed using a plasma atomic layer deposition. A first cycle comprising a stage of supplying a first source and a stage of purging the first source and a second cycle comprising a stage of supplying a second source and a stage of purging the second source may be performed at least once during the formation of the second layer. Thereafter, plasma may be applied in a state where a reactant has been provided. In addition or alternatively, a third layer may be formed on the second layer (see FIG. 8E). The third layer may be formed using a different deposition process using plasma.

After the formation of the second layer and/or the third layer, a dopant may be diffused in operation S5 (see FIG. 8F). This stage may be carried out by using the second layer containing the dopant. For example, a doped region may be formed inside the structure by applying energy to the second layer comprising the dopant.

The diffusing of the dopant S5 may be omitted. In other words, a different process such as patterning the second layer or forming an additional layer may be performed after the formation of the second layer.

When the second layer functions as a diffusion source layer to form the doped region, the dopant may be diffused into the inside of the structure by applying energy (see FIG. 8F). In this case, the remnant of the first layer is located between the second layer and the structure, thereby preventing the diffusion of the dopant. In other words, dopant may not be diffused in a portion of the structure corresponding to the remnant of the first layer.

The diffusing of the dopant by applying energy may be implemented by annealing. The application of energy may be performed using various processes such as rapid thermal annealing (RTA), rapid thermal processing (RTP), and ultraviolet (UV) light application. A doping concentration of the structure may be controlled by controlling at least one of the parameters of the above processes.

A third layer may be formed on the second layer (see FIG. 8E) between the forming of the second layer in operation S4 and the diffusing of the dopant into the structure using annealing in operation S5. The third layer may be a capping layer which prevents the dopant of the second layer from being volatilized and lost into a reaction space or from being diffused into a neighboring film.

The third layer may be formed using a plasma atomic layer deposition process. A cycle comprising a stage of supplying a source and a stage of applying plasma in a state where a reactant has been provided may be performed at least once during the formation of the third layer. Purging may also be performed between the stage of supplying the source and the stage of applying the plasma and/or between cycles. The third layer may be formed using a different deposition process.

After the dopant is diffused in operation S5, the remnant of the first layer and the second layer may be removed. When the first layer and the second layer are formed of the same material or have the same etch selectivities, both the remnant of the first layer and the second layer may be removed using a single etching step (i.e., a single etching material). When the first layer and the second layer are formed of different materials or have different etch selectivities, the remnant of the first layer and the second layer may be removed using at least two etching steps (i.e., at least two etching materials).

Alternatively, when the third layer has been formed on the second layer, an operation of removing the remnant of the first layer, the second layer, and the third layer may be performed. At this time, the first layer may be a silicon nitride layer functioning as a diffusion barrier, the second layer may be a silicate glass layer functioning as a diffusion source layer, and the third layer may be a silicon oxide layer functioning as a capping layer. In this case, the second and third layers, i.e., oxide layers, may be removed in a first etching step and the remnant of the first layer may be removed in a second etching step.

After the first etching step, an exposed surface of the structure may be damaged during the second etching step. When the structure and the remnant of the first layer on the structure are exposed after the second layer or the second and third layers are removed, two steps may be performed during the second etching step to prevent damage to the exposed surface of the structure: a step of forming a fourth layer with the same material as the first layer on the exposed surface of the structure and the remnant of the first layer; and a step of simultaneously removing the remnant of the first layer and the fourth layer.

The steps described above are to prevent damages. The fourth layer may be formed to be densified on the exposed surface of the structure using an ion bombardment effect and/or to be embrittled on the remnant of the first layer using a hydrogen active species. Accordingly, a first part of the fourth layer on the exposed surface of the structure has a lower etch rate than a second part of the fourth layer on the remnant of the first layer in a following etching process. As a result, the remnant of the first layer may be removed without the structure being damaged during the second etching step.

Although it is assumed that the first layer is a nitride layer and the second and third layers are oxide layers in the above description of the second etching step, the inventive concept should not be limited thereto. The third layer may be omitted and the technical spirit of the inventive concept may be applied when the first and second layers have different etch selectivities. In addition, when etching is performed on the exposed surface of the structure and the first layer remaining on the structure, the technical spirit of the inventive concept may be applied to prevent the exposed surface of the structure from being overetched. In other words, the exposed surface of the structure may be prevented from being damaged by forming the fourth layer (partially densified or embrittled) with the same material as the first layer on the remnant of the first layer and then etching the first layer and the fourth layer at the same time.

FIGS. 2 and 3 schematically show methods of processing a substrate according to embodiments of the inventive concept. These methods may be modifications of the method of processing a substrate according to the embodiments described above. The redundant descriptions of the embodiments will be omitted.

Referring to FIG. 2, a diffusion barrier is formed on a structure in operation S11. The structure may be a patterned structure. In addition, the structure may comprise a first surface and a second surface having a slope with respect to the first surface. For example, the diffusion barrier may be formed to comprise a first portion and a second portion having a slope with respect to the first portion.

As described above, the diffusion barrier may be formed so that part (e.g., the first portion or the second portion) of the diffusion barrier is densified or embrittled. To obtain such diffusion barrier, plasma may be applied while the diffusion barrier is being formed. As a result, the diffusion barrier may have different physical properties at different positions. The application of plasma may be performed after the diffusion barrier is formed in operation S12 (FIG. 2) or may be performed while the diffusion barrier is being formed in operation S21 (FIG. 3).

Thereafter, the diffusion barrier is isotropically etched in operation S13. Although isotropic etching is performed, selective etching of the diffusion barrier may be accomplished since the diffusion barrier has different physical properties at different positions.

For example, the first portion may be densified by the application of plasma. In this case, the first portion may remain while the second portion may be removed after the isotropic etching. In another example, the first portion may be embrittled by the application of plasma. In this case, the first portion may be removed while the second portion may remain after the isotropic etching.

Thereafter, a diffusion source layer is formed on the structure and a remnant of the diffusion barrier in operation S14. As a result, the diffusion barrier may directly contact one of the first and second surfaces of the structure and the diffusion source layer may directly contact the other.

For example, the diffusion source layer may be formed in a state where the first portion (i.e., the portion corresponding to the first surface of the structure) of the diffusion barrier has been densified and remained after wet etching. In this case, the diffusion barrier may directly contact the first surface of the structure and the diffusion source layer may directly contact the second surface of the structure.

After the diffusion source layer is formed, energy is applied in operation S15. A dopant is diffused into the structure through the application of energy. The diffusion of a dopant may be performed in a selective region based on the remnant of the diffusion barrier. Thereafter, the diffusion source layer and the diffusion barrier are removed in operation S16.

FIG. 3 shows a modification of the embodiments illustrated in FIG. 2. The modification shown in FIG. 3 is substantially the same as the embodiments shown in FIG. 2, with the exception that the application of plasma is performed while the diffusion barrier is being formed in operation S21. In other words, according to the embodiments shown in FIG. 3, plasma may be used while the diffusion barrier is being formed in operation S21, and therefore, the diffusion barrier having different physical properties at different positions may be formed.

FIG. 4 schematically shows a method of processing a substrate according to embodiments of the inventive concept. The method may be a modification of the method of processing a substrate according to the embodiments described above. The redundant descriptions of the embodiments will be omitted.

Referring to FIG. 4, a silicon substrate having a step structure is formed in operation S101. Subsequently, a silicon nitride layer is deposited on the step structure in operation S201. The silicon nitride layer is deposited at a temperature of 450 and 550° C. using plasma enhanced atomic layer deposition (PEALD). However, the silicon nitride layer may be deposited using thermal ALD, thermal chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), or cyclic PECVD.

Thereafter, wet cleaning is performed on the silicon nitride layer in operation S301. The wet cleaning is performed by dipping the silicon nitride layer in a diluted hydrofluoric acid (DHF) solution, in which a ration of HF:H₂O is 1:100 or 1:200, for about 1 to 5 minutes. A wet cleaning rate may be changed by changing the ratio of HF:H₂O or a different cleaning solution may be used. Part of the silicon nitride layer is selectively removed during the wet cleaning.

Thereafter, a boron silicate glass (BSG)/phosphorous silicate glass (PSG) layer is deposited on the silicon nitride layer, which has been partially removed, in operation S401. At this time, the BSG/PSG layer is deposited using PEALD. However, a BSG layer or a PSG layer may be deposited using thermal ALD, thermal CVD, PECVD, or cyclic PECVD. Either BSG or PSG may be deposited separately or both BSG and PSG may be deposited together or may be deposited alternately and sequentially until the target thickness is achieved.

After the BSG/PSG layer is deposited, a capping oxide layer is deposited in operation S501. At this time, a SiO₂ layer is deposited as the capping oxide layer using PEALD. However, the capping oxide layer may be deposited using thermal ALD, thermal CVD, PECVD, or cyclic PECVD. The capping oxide layer prevents a boron or phosphorous element of the BSG/PSG layer after its deposition from being volatilized and lost into a surrounding reaction space or diffused into a neighboring film. The deposition of the BSG/PSG layer and the deposition of the capping oxide layer may be performed at a temperature of 300° C. Alternatively, the deposition of the BSG/PSG layer and the deposition of the capping oxide layer may be performed in situ in one reactor and may furthermore be performed without vacuum brake.

After the capping oxide layer is formed, annealing is performed in operation S601. At this time, the annealing is performed at a temperature of 800° C. in a nitrogen (or N₂) atmosphere for two hours. However, process parameters of the annealing may be adjusted. For example, rapid thermal processing, such as RTP (Rapid Thermal Processing) or RTA (Rapid Thermal Annealing), performed for a short time may be used. In some embodiments, rapid high-temperature annealing may be performed or energy may be applied under UV light using UV processing instead of thermal processing. Besides, other activation means which activate diffusion of a P component in the PSG layer may be used.

Through the annealing, a boron or phosphorous component in the BSG/PSG layer is diffused in operation S701. In detail, the boron and phosphorous components may be diffused into the step structure through the surface of the step structure from which the silicon nitride layer has been removed after the wet cleaning. Thereafter, the capping oxide layer and a remnant of the silicon nitride layer are removed using an etching solution (e.g., DHF) in operation S801.

FIG. 5 shows an example of a deposition method used when the silicon nitride layer is deposited in operation S201 shown in FIG. 4. PEALD is performed using Si source supply (t1)/Si source purging (t2)/reactant pre-flow (t3)/radio frequency (RF) plasma application (t4)/reactant purging (t5) as a basic cycle. The silicon nitride layer is formed to a thickness of 100 angstroms (i.e., 10 nm) by repeating the basic cycles (for example, “m” times where “m” is at least 1).

Since there is a reactant pre-flow step, a reactant gas may be uniformly distributed in a reaction space before plasma is supplied to the reaction space. Accordingly, active species may be uniformly distributed in the plasma supply step, so that a stable process is accomplished.

Referring back to FIG. 5, an Ar purge gas may be continuously supplied to the reaction space. Dichlorosilane (DCS), i.e., SiH₂Cl₂, is used as a Si source and a nitrogen substance containing hydrogen, e.g., ammonia (NH₃), is used as a reactant.

The Si source is not limited to the DCS. Apart from the DCS source, TSA, (SiH3)3N; DSO, (SiH3)2; DSMA, (SiH3)2NMe; DSEA, (SiH3)2NEt; DSIPA, (SiH3)2N(iPr); DSTBA, (SiH3)2N(tBu); DEAS, SiH3NEt2; DIPAS, SiH3N(iPr)2; DTBAS, SiH3N(tBu)2; BDEAS, SiH2(NEt2)2; BDMAS, SiH2(NMe2)2; BTBAS, SiH2(NHtBu)2; BITS, SiH2(NHSiMe3)2; TEOS, Si(OEt)4; SiC14; HCD, Si2Cl6; 3DMAS, SiH(N(Me)2)3; BEMAS, Si H2[N(Et)(Me)]2; AHEAD, Si2 (NHEt)6; TEAS, Si(NHEt)4; and Si3H8 may be used as the Si sources. At least one of these Si sources may be included when the Si source is supplied.

The reactant is not limited to ammonia. Apart from NH₃, NH₄+ may be used as a nitrogen substance containing hydrogen. As well as a type of a nitrogen reactant containing hydrogen, a flow rate of sources and/or the reactant may also be adjusted.

For example, when an ammonia gas is supplied, two different conditions of 100 sccm and 250 sccm may be used. In other words, when there is a difference in the flow rate of ammonia, i.e., a difference in the amount of hydrogen elements supplied to a reactor, an influence exerted on wet cleaning of a thin film on the patterned structure may be adjusted and selective etching may be accomplished.

FIG. 6 shows an embodiment of operation S401 shown in FIG. 4 in which the BSG/PSG layer is deposited. FIG. 6 shows steps for independently forming a PSG layer. In the embodiment shown in FIG. 6, the PSG layer may be formed using PEALD, which comprises a first cycle STEP1 of Si source supply (t1)/Si source purging (t2) and a second cycle STEP2 of P source supply (t3)/P source purging (t4)/RF plasma application (t5)/purging (t6). The first cycle STEP1 may be repeated “m” times (where “m” is at least 1) and the second cycle STEP2 may be repeated “n” times (where “n” is at least 1).

An oxygen gas may be used as a reactant. The reactant may be continuously supplied to a reaction space during the deposition. An Ar purge gas may also be continuously supplied to the reaction space during the deposition.

The oxygen gas may react with the Si source and the P source only when the oxygen gas is activated by plasma. In this case, only oxygen gas may be continuously supplied without the Ar purge gas being supplied. In other words, the oxygen gas may be used as a reactive purge gas functioning as both a reactant gas and a purge gas. Alternatively, the oxygen gas may be supplied during only the first cycle STEP1 or the second cycle STEP2. As another alternative, thermal ALD may be performed in the first cycle STEP1 and the second cycle STEP2 and then plasma post-treatment may be performed.

Referring to FIG. 6, a Si-containing source is chemically adsorbed to a sub-layer on a substrate in the first cycle STEP1. Thereafter, a P-containing source is supplied to the substrate in the second cycle STEP2 to be chemically combined with the Si-containing source and then react with an activated oxygen radical, thereby forming a PSG film.

The first cycle STEP1 for chemically combining a Si source with a sub-layer may be repeated “m” times. The second cycle STEP2 for chemically combining a P source with the Si source on a substrate and forming a PSG film using oxygen plasma may be repeated “n” times. A ratio of silicon to phosphorous in a PSG layer may be controlled by adjusting the numbers of repetitions of the first cycle STEP1 and the second cycle STEP2. Accordingly, the concentration of a P component diffused to the substrate may be controlled during annealing.

In the embodiment shown in FIG. 6, the first cycle STEP1 is repeated one time and the second cycle STEP2 is repeated five times (i.e., m=1 and n=5 corresponding to a CK5 condition) so that a PSG layer is deposited to a thickness of 50 angstroms (i.e., 5 nm). Here, CK is an abbreviation for control knob and indicates a ratio of the number of repetitions of the first cycle STEP1 and the number of repetitions of the second cycle STEP2. In other words, CK5 indicates that the ratio of the number of repetitions of the first cycle STEP1 and the number of repetitions of the second cycle STEP2 is 1:5. However, a CK ratio may be changed in various ways and the concentration of a P component may be adjusted according to the CK ratio. In the current embodiment, an organometallic precursor containing a P component may be used as a source containing a P component.

FIG. 7 shows a detailed deposition method used when the capping oxide layer is deposited in operation S501 shown in FIG. 4. The capping oxide layer may be deposited to prevent a P component from being volatilized and lost into a surrounding reaction space or diffused into a neighboring film from the PSG layer which has been previously deposited.

The capping oxide layer may be formed using PEALD. The BSG/PSG layer and the capping oxide layer may be deposited at the same temperature in operations S401 and S501. Operations S401 and S501 may be performed in situ in one reactor without vacuum brake. In the current embodiment, the BSG/PSG layer and the capping oxide layer are sequentially deposited in situ in one reaction chamber at a temperature of 300° C.

Referring to FIG. 7, a cycle of Si source supply (t1)/Si source purging (t2)/RF plasma application (t3)/purging (t4) may be repeated multiple times (e.g., “x” times where “x” is at least 1) to deposit the capping oxide layer. An oxygen gas may participate as a reactant gas when activated by plasma. For example, an oxygen gas may participate as a component of a SiO₂ film when activated by plasma. When plasma is not supplied, an oxygen gas may function as a purge gas without reacting with a Si source.

The above-described various substances may be used as the Si source to form the capping oxide layer. An oxygen source may comprise at least one of ozone (O₃), N₂O, and NO besides O₂. In the current embodiment, the capping oxide layer is deposited to a thickness of 100 angstroms (i.e., 10 nm).

Since the silicon nitride layer, the PSG layer, and the capping oxide layer are deposited at different temperature, the silicon nitride layer is deposited on the substrate in a first reactor, the substrate is transferred to a second reactor in which a PSG process is performed without vacuum brake, and the PSG layer and the capping oxide layer are sequentially formed in the second reactor. However, the silicon nitride layer, the PSG layer, and the capping oxide layer may be deposited in situ in one reactor.

FIGS. 8A through 8H are schematic diagrams of a method of processing a substrate, according to one or more embodiments of the inventive concept. The method shown in FIGS. 8A through 8H may be a modification of the methods of processing a substrate according to the above-described embodiments. The redundant descriptions of the embodiments will be omitted.

Referring to FIG. 8A, the method is performed on a step structure 510 on a substrate. Referring to FIG. 8B, a silicon nitride layer 520 is deposited on the substrate having the step structure 510 at a temperature of 450° C., with supply of 100 sccm NH₃, using PEALD. Referring to FIG. 8C, wet cleaning is performed using a DHF solution to remove a portion of the silicon nitride layer 520 which has been deposited on the side of the step structure 510. Despite the wet cleaning, a portion of the silicon nitride layer 520 which has been deposited on the top of the step structure 510 remains as a remnant silicon nitride layer 520′.

When a plasma process is performed (e.g., when a direct plasma or an in-situ plasma process is performed) in a reactor, plasma active species have directivity. Due to this directivity, a deposited film is densified and hardened at the top or bottom of the step structure 510 by an ion bombardment effect of the active species. On the contrary, this bombardment effect is relatively weak at the side of the step structure 510, and therefore, a film deposited on the side of the step structure 510 is less hardened than the film deposited on the top or bottom of the step structure 510. In other words, a film deposited on a surface perpendicular to the traveling direction of plasma active species is harder than a film deposited on a surface parallel to the traveling direction thereof.

Accordingly, when wet cleaning is performed on the silicon nitride layer 520 (see FIG. 8B) deposited on a pattern using a plasma process, a film deposited on the top and the bottom of the pattern remains while a film deposited on the side thereof is removed (see FIG. 8C).

Referring to FIGS. 8D and 8E, a PSG layer 530 and a capping oxide layer 540 are sequentially deposited. Referring to FIG. 8F, annealing is performed. A P component in the PSG layer 530 is diffused into the step structure 510 of the substrate through the annealing, thereby forming a doped region 550S. As shown in FIG. 8G, the capping oxide layer 540 is removed using wet cleaning. As shown in FIG. 8H, the remnant silicon nitride layer 520′ on the top of the step structure 510 is removed.

According to the embodiments shown in FIGS. 8A through 8H, a P component is blocked from being diffused into a pattern at the top of the pattern on which a silicon nitride layer remains while the P component is diffused into the pattern at the side of the pattern on which the silicon nitride layer does not exist. Accordingly, a particular portion in the pattern may be selectively doped. This selective doping may be used for side doping of shallow trench isolation (STI) for a transistor, doping of a p-poly Si film of a VNAND device, and so on.

FIGS. 9A through 9H are schematic diagrams of a method of processing a substrate, according to one or more embodiments of the inventive concept. The method shown in FIGS. 9A through 9H may be a modification of the methods of processing a substrate according to the above-described embodiments. The redundant descriptions of the embodiments will be omitted.

Unlike the embodiments shown in FIGS. 8A through 8H, the silicon nitride layer 520 is deposited at a temperature of 550° C., with supply of 250 sccm NH₃, using PEALD (FIG. 9B) in the embodiments shown in FIGS. 9A through 9H. Thereafter, wet cleaning (FIG. 9C), deposition of the PSG layer 530 (FIG. 9D), deposition of the capping oxide layer 540 (FIG. 9E), P component doping (FIG. 9F), removing of the capping oxide layer 540 and the PSG layer 530 (FIG. 9G), and removing of a remnant silicon nitride layer 520″ (FIG. 9H) are sequentially performed.

Apart from process conditions used when the silicon nitride layer 520 is deposited, other process conditions used in the embodiments shown in FIGS. 9A through 9H may be the same as those used in the embodiments shown in FIGS. 8A through 8H. In the embodiments shown in FIGS. 8A through 8H, when wet cleaning is performed on the silicon nitride layer 520 after the silicon nitride layer 520 is deposited on a pattern, a portion of the silicon nitride layer 520 deposited on the side of the pattern is etched while a portion of the silicon nitride layer 520 deposited on the top of the pattern remains. On the contrary, in the embodiments shown in FIGS. 9A through 9H, a portion of the silicon nitride layer 520 deposited on the top of the pattern is etched while a portion of the silicon nitride layer 520 deposited on the side of the pattern remains. Accordingly, a doped region 550U is formed at the top of the pattern.

This phenomenon is related to hydrogen content in a silicon nitride layer at a different position. While 100 sccm NH₃ is supplied when the silicon nitride layer is formed in the embodiments shown in FIGS. 8A through 8H, more NH₃, i.e., 250 sccm NH₃ is supplied in the embodiments shown in FIGS. 9A through 9H. Accordingly, when NH₃ is excited by plasma in the embodiments shown in FIGS. 9A through 9H, more hydrogen ions are generated in the embodiments shown in FIGS. 9A through 9H than in the embodiments shown in FIGS. 8A through 8H, and hydrogen contained in the silicon nitride layer deposited on the top and the bottom located in a direction perpendicular to the traveling direction of hydrogen active species is more than hydrogen contained in the silicon nitride layer deposited on the side due to the directivity of the active species. As a result, a wet etch rate of the top is higher than a wet etch rate of the side, and therefore, the silicon nitride layer is removed faster from the top than from the side in the embodiments shown in FIGS. 9A through 9H.

On the contrary, when NH₃ is excited by plasma in the embodiments shown in FIGS. 8A through 8H, a wet etch rate (WER) of a silicon nitride layer is more influenced by an ion bombardment effect of plasma active species than a hydrogen content in the silicon nitride layer due to relatively fewer hydrogen ions. As a result, the silicon nitride layer is removed faster from the side of a pattern than from the top of the pattern, as described above.

FIGS. 10 and 11 are transmission electron microscopy (TEM) photographs of the results of performing wet cleaning after depositing a silicon nitride layer on a pattern in the embodiments (100 sccm NH₃) shown in FIGS. 8A through 8H and in the embodiments (250 sccm NH₃) shown in FIGS. 9A through 9H.

FIG. 10 shows that the silicon nitride layer remains at the top and the bottom of the pattern, which are located in a direction perpendicular to the traveling direction of plasma active species, after the wet etching of the silicon nitride layer. In other words, it can be seen that an ion bombardment effect is a major dominant factor in the etching of the silicon nitride layer.

It can be seen in FIG. 11 that the silicon nitride layer deposited on the top and the bottom of the pattern to contain relatively more hydrogen is removed faster than the silicon nitride layer deposited on the side to contain relative less hydrogen. In other words, it can be seen that a hydrogen content in a thin film is a major dominant factor in the etching of the silicon nitride layer.

As shown in FIGS. 10 and 11, either an ion bombardment effect or a hydrogen content may be selected, as a factor controlling wet cleaning conditions for a film deposited on a pattern, by controlling a flow rate of a nitrogen reactant gas containing hydrogen which is supplied to a reaction space.

Although the embodiments have been described based on the fact that a silicon nitride layer is used as a diffusion barrier, the inventive concept is not limited thereto. The embodiments are provided to accomplish etching and doping with respect to a particular portion of a pattern. For example, when a plasma process is performed on the pattern, a dominant factor in wet cleaning of a film deposited on the pattern is determined by controlling a flow rate of a reactant containing hydrogen. In other words, either an ion bombardment effect or a hydrogen content may be selected as the dominant factor.

For example, the higher the flow rate of a reactant containing hydrogen, it is more likely that a hydrogen content in a film is a dominant factor in wet cleaning. As a result, selective cleaning or selective doping may be accomplished at particular portions, e.g., the top and the bottom, of a pattern using a local difference in the hydrogen content in the film on a substrate having a step difference and the directivity of hydrogen ions comprised in the reactant gas.

According to some embodiments of the inventive concept, a doping level in a substrate may be controlled by controlling a deposition condition of a doped film and an annealing condition. Furthermore, a doping level by portion within a substrate may be controlled to be different.

FIG. 12 is a diagram of a secondary ion mass spectroscopy (SIMS) result showing P concentrations in a pattern before/after annealing according to existence or non-existence of a silicon nitride layer.

Referring to FIG. 12, sample #01 (POR) and sample #02 (POR) correspond to a case where a PSG layer is deposited without a silicon nitride layer. In this case, the PSG layer is deposited on the side of a pattern after wet cleaning. Sample #03 (SiN) and sample #04 (SiN) correspond to a case where a PSG layer is deposited on a silicon nitride layer. In this case, the PSG layer is deposited on the silicon nitride layer remaining on the top of the pattern after wet cleaning. Samples #01 and #03 represent the distribution of P concentrations right after the deposition of the PSG layer (As-dep.) and samples #01 and #03 represent the distribution of P concentrations after annealing is performed after the deposition of the PSG layer (Anneal).

In the experiments, annealing was performed at a temperature of 800° C. in a nitrogen atmosphere for four hours. As shown in FIG. 12, a P component was not detected in the pattern right after the deposition of the PSG layer in both samples #01 and #03. However, after the annealing, a P component was detected in the pattern in only sample #02 corresponding to the case of non-existence of the silicon nitride layer between samples #02 and #04. Accordingly, it can be seen that the silicon nitride layer functions as a diffusion barrier against diffusion of the P component. In addition, it can be seen from the result that doping may be performed on a particular portion (e.g., the side) of the pattern.

FIGS. 13 through 18 are schematic diagrams of a method of processing a substrate, according to one or more embodiments of the inventive concept. The method may be a modification of the method of processing a substrate according to the embodiments described above. The redundant descriptions of the embodiments will be omitted.

Referring to FIG. 13, a plurality of stack structures may be formed on a substrate 200. The stack structure may comprise a lower layer 210 and an upper layer 220 alternately stacked on the substrate 200. Each of the lower layers 210 may be an insulating layer and each of the upper layers 220 may be a conductive layer. Alternatively, each of the lower layers 210 may be a first sacrificial layer and each of the upper layers 220 may be a second sacrificial layer. Thereafter, a buffer layer 230 is formed on the stack structure and holes are formed by etching the lower layers 210, the upper layers 220, and the buffer layer 230, so that the substrate 200 has a patterned structure.

Thereafter, referring to FIG. 14, a diffusion barrier 710 is formed on the substrate 200 having the patterned structure, using plasma deposition method. A large amount of hydrogen may be contained in a reactant supplied during the formation of the diffusion barrier 710, and therefore, a hydrogen content in the patterned structure will be a dominant factor in wet cleaning performed later.

Referring to FIG. 15, the diffusion barrier 710 is removed using isotropic etching like wet etching so that only part of the diffusion barrier 710 remains. In detail, the diffusion barrier 710 is selectively removed from the top and bottom surfaces of the patterned structure which have a high hydrogen content due to hydrogen active species applied in a vertical direction during a plasma process. On the contrary, the diffusion barrier 710 on the side surface of the patterned structure remains as a remnant diffusion barrier 710′.

The remnant diffusion barrier 710′ on the side surface may be separated from the substrate 200. For example, the remnant diffusion barrier 710′ may have a slanting surface I at the bottom thereof and the slanting surface I may not contact the top of the substrate 200. As a result, part of a lower layer 210 in the stack structure may be exposed.

Referring to FIG. 16, a diffusion source layer 720 is formed on the patterned structure and the remnant diffusion barrier 710′. When the remnant diffusion barrier 710′ is separated from the substrate 200, the diffusion source layer 720 may contact the side of the lower layer 210 of the stack structure.

Referring to FIG. 17, energy is applied to the diffusion source layer 720, so that a doped region 730 may be formed inward from the top surface of the patterned structure and the bottom surface thereof (i.e., the top surface of the substrate 200). Although not shown, a capping insulating layer may be formed on the diffusion source layer 720 before energy is applied to the diffusion source layer 720 to enable the diffusion source layer 720 to efficiently function.

Referring to FIG. 18, the diffusion source layer 720, the remnant diffusion barrier 710′, and the buffer layer 230 are removed and an insulating layer 240 is formed to fill the holes. As a result, the doped region 730 is realized in a particular region of the patterned structure.

FIGS. 19A through 20C are schematic diagrams of methods of processing a substrate according to one or more embodiments of the inventive concept. The methods shown in FIGS. 19A through 20C may be modifications of the methods of processing a substrate according to the above-described embodiments. The redundant descriptions of the embodiments will be omitted.

The method shown in FIGS. 19A through 19C may be a modification of the method of processing a substrate according to the embodiment shown in FIGS. 8A through 8H. Referring to FIGS. 8A through 8F, embodiments of the inventive concept may comprise preparing a structure having a first surface and a second surface (see FIG. 8A), forming a diffusion barrier (e.g., a silicon nitride layer) on the structure (see FIG. 8B), isotropically etching the diffusion barrier (see FIG. 8C), forming a diffusion source layer (e.g., a BSG/PSG layer) on the structure and the remnant diffusion barrier 520′ (see FIG. 8D), diffusing a dopant (see FIG. 8F), and removing the diffusion source layer (see FIGS. 8G and 19A).

After the diffusion source layer is removed, a side of the structure on the substrate may be exposed (see FIG. 19A). At this time, damage may occur to the exposed side and an impurity region 750S while a remnant diffusion barrier 710U is being etched in a following process. To prevent the damage, a damage protection layer 770 may be formed on the exposed side of the structure and the remnant diffusion barrier 710U (see FIG. 19B). The damage protection layer 770 may be formed of substantially the same material as the diffusion barrier. Since a reactant containing a large amount of hydrogen is supplied during the formation of the damage protection layer 770, the damage protection layer 770 on the top of the structure (i.e., on the remnant diffusion barrier 710U) may be embrittled.

Thereafter, the remnant diffusion barrier 710U and the damage protection layer 770 are simultaneously removed (see FIG. 19C). Since an upper portion 770U of the damage protection layer 770 is more brittle than a side portion 770S of the damage protection layer 770, a single layer, i.e., the side portion 770S, on the side of the structure and a multi-layer, i.e., the remnant diffusion barrier 710U and the upper portion 770U, on the top of the structure may be uniformly etched using isotropic etching despite the thickness of the multi-layer on the top of the structure. Accordingly, the remnant diffusion barrier 710U may be removed without damaging the structure. In other words, since a top part is thick but has low etch resistance while a side part is thin but has high etch resistance, wet etching from a surface of the upper portion 770U of the damage protection layer 770 to the surface of the structure and wet etching from a surface of the side portion 770S thereof to the surface of the structure may be controlled to be performed for the same period of time and completed substantially at the same time using a difference in a wet etch rate between the top part and the side part.

The method shown in FIGS. 20A through 20C may be a modification of the method of processing a substrate according to the embodiment shown in FIGS. 9A through 9H. Referring to FIGS. 9A through 9F, embodiments of the inventive concept may comprise preparing a structure having a first surface and a second surface (see FIG. 9A), forming a diffusion barrier on the structure (see FIG. 9B), isotropically etching the diffusion barrier (see FIG. 9C), forming a diffusion source layer on the structure and the remnant diffusion barrier 520″ (see FIG. 9D), diffusing a dopant (see FIG. 9F), and removing the diffusion source layer (see FIGS. 9G and 20A).

After the diffusion source layer is removed, a top of the structure on the substrate may be exposed (see FIG. 20A). At this time, damage may occur to the exposed top and an impurity region 750U while a remnant diffusion barrier 710S is being etched in a following process. To prevent the damage, the damage protection layer 770 may be formed on the exposed top of the structure and the remnant diffusion barrier 710S (see FIG. 20B). Since a reactant containing no hydrogen is supplied during the formation of the damage protection layer 770, the damage protection layer 770 on the top of the structure may be densified.

Thereafter, the remnant diffusion barrier 710S and the damage protection layer 770 are simultaneously removed (see FIG. 20C). Since the upper portion 770U of the damage protection layer 770 is denser than the side portion 770S of the damage protection layer 770, a multi-layer, i.e., the remnant diffusion barrier 710S and the side portion 770S, on the side of the structure and a single layer, i.e., the upper portion 770U, on the top of the structure may be uniformly etched using isotropic etching despite the thickness of the multi-layer on the side of the structure. Accordingly, the remnant diffusion barrier 710S may be removed without damaging the structure. In other words, since a top part is thin but has high etch resistance while a side part is thick but has low etch resistance, wet etching from a surface of the upper portion 770U of the damage protection layer 770 to the surface of the structure and wet etching from a surface of the side portion 770S thereof to the surface of the structure may be controlled to be performed for the same period of time and completed substantially at the same time using a difference in a wet etch rate between the top part and the side part.

It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.

While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the following claims. 

What is claimed is:
 1. A method of processing a substrate, the method comprising: preparing a structure comprising a first surface and a second surface having a slope with respect to the first surface; forming a first layer on the structure by applying plasma, wherein at least part of the first layer is densified or embrittled due to collision of plasma active species; isotropically etching the first layer so that at least part of the first layer remains as a remnant; forming a second layer on the structure and the remnant of the first layer, the second layer comprising a dopant; and diffusing the dopant into the structure.
 2. The method of claim 1, wherein the dopant is not diffused to a portion of the structure corresponding to the remnant of the first layer.
 3. The method of claim 1, wherein the forming of the first layer and the isotropic etching of the first layer result in selective etching of the first layer without a photolithography process.
 4. The method of claim 1, wherein a location of the remnant of the first layer is controlled by an amount of hydrogen active species during the forming of the first layer.
 5. The method of claim 1, wherein the first layer on the first surface that is densified or not embrittled is maintained and the first layer on the second surface that is not densified or embrittled is removed by the isotropic etching.
 6. The method of claim 5, wherein the first layer on the first surface is densified due to an ion bombardment effect.
 7. The method of claim 1, wherein an etch rate the first layer on the first surface is slower than an etch rate of the first layer on the second surface during the isotropic etching.
 8. The method of claim 7, wherein the first layer on the first surface is removed due to hydrogen active species injected during the applying of the plasma.
 9. The method of claim 1, further comprising forming a third layer on the second layer between the forming of the second layer and the diffusing of the dopant.
 10. The method of claim 1, wherein the first layer comprises a silicon nitride layer and the second layer comprises a silicate glass layer.
 11. The method of claim 1, further comprising removing the remnant of the first layer and the second layer.
 12. The method of claim 11, wherein the first layer and the second layer comprise different materials, and the removing of the remnant of the first layer and the second layer comprises: removing the second layer to expose the structure and the remnant of the first layer on the structure; forming a fourth layer on an exposed surface of the structure and the remnant of the first layer, using the same material as the first layer; and removing the remnant of the first layer and the fourth layer.
 13. The method of claim 12, wherein plasma is applied during the forming of the fourth layer to densify or embrittle at least part of the fourth layer.
 14. The method of claim 1, wherein the forming of the second layer comprises a first cycle and a second cycle, wherein the first cycle comprises: supplying a first source; and purging the first source, and the second cycle comprises: supplying a second source; and purging the second source, and wherein the second cycle further comprises applying plasma in a state where a reactant has been provided.
 15. A method of processing a substrate, the method comprising: forming a diffusion barrier, comprising a first portion and a second portion having a slope with respect to the first portion, on a structure; applying plasma to densify or embrittle the first portion of the diffusion barrier; isotropically etching the diffusion barrier; forming a diffusion source layer on the structure and a remnant of the diffusion barrier; diffusing a dopant into the structure; and removing the diffusion source layer and the remnant of the diffusion barrier.
 16. The method of claim 15, wherein the first portion is densified during the applying of the plasma, and the first portion remains and the second portion is removed after the isotropic etching.
 17. The method of claim 15, wherein the first portion is embrittled during the applying of the plasma, and the first portion is removed and the second portion remains after the isotropic etching.
 18. The method of claim 15, wherein the applying of the plasma is performed during the forming of the diffusion barrier.
 19. The method of claim 15, wherein the structure comprises a first surface and a second surface, the diffusion barrier directly contacts one of the first and second surfaces, and the diffusion source layer directly contacts the other of the first and second surfaces.
 20. A method of processing a substrate, the method comprising: forming a diffusion barrier on the substrate having a patterned structure using plasma deposition method; removing the diffusion barrier except for a part of the diffusion barrier using wet etching; forming a diffusion source layer on the patterned structure and the part of the diffusion barrier; and applying energy to the diffusion source layer. 